A ZEKE photoelectron spectroscopy and ab initio study of the cis- and trans-isomers of formanilide: Characterizing the cationic amide bond?

S Ullrich, G Tarczay, X Tong, C E H Dessent, K Muller-Dethlefs

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Abstract

The cis- and trans-conformational isomers of formanilide, an aromatic amide which represents a model peptide, have been studied using zero electron kinetic energy (ZEKE) spectroscopy to investigate the properties of cationic amides. Accurate ionization energies of 67 408 and 67 710 +/- 5 cm(-1) were measured for the trans- and cis-isomers respectively, allowing the trams-conformation to be assigned as the lower energy conformation in the Do state. For trams-formanilide, the ZEKE spectra are dominated by excitation of the in-plane side-arm bend (211 cm(-1)) and the amide stretch (952 cm(-1)), while the cis-formanilide spectra are dominated by the out-of-plane side-arm bend (80 cm(-1)) and the C-1-N torsion (126 cm(-1)). Ab initio (HF/MP2) and CASSCF calculations are presented to support the experimental observations.

Original languageEnglish
Pages (from-to)5450-5458
Number of pages9
JournalPhysical Chemistry Chemical Physics
Volume3
Issue number24
Publication statusPublished - 15 Dec 2001

Keywords

  • CORRELATED MOLECULAR CALCULATIONS
  • GAUSSIAN-BASIS SETS
  • N-PHENYL FORMAMIDE
  • FLUORESCENCE SPECTROSCOPY
  • CHARGE DELOCALIZATION
  • HYDRATED CLUSTERS
  • HYDROGEN
  • IONIZATION
  • VIBRATIONS
  • COMPLEXES

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